I think the reason definitions and categories are breaking down in this discussion is simply because many of these distinctions simply don't apply, any more. Maybe they're simply not descriptive enough. Someone's game is only partly defined by where they stand on the court. There's also:

For example, you could simply describe Coria and Gaudio as clay courters, but one gets by on fitness and attitude and a whole lot of moxie while the other does it on talent and hot streaks and pouts the rest of the time. The techincal details are probably the least interesting parts of that discussion, comparatively.